Mr. Meles' Youtube Channel

You can find the Putt-Putt video playlist here. There are other interesting Science and Math videos here too!

https://www.youtube.com/user/TheMrMeles

Thermal Energy Transfer: Radiation

Radiation

·        Radiant energy is the transfer of energy by invisible waves given off by the energy source

·        These invisible waves are called infrared waves (a type of electromagnetic wave from the sun)

·        Infrared waves are given off by all heat sources, including you

·        Heat is radiant energy from the sun that reaches your skin

·        Radiant energy warms up objects when the waves of radiant energy come into contact with matter making the particles vibrate faster

Answers to Radiation Worksheet

1) Radiation waves are absorbed by the person in front of you so you do not feel the heat.

2) White clothing reflects infrared radiation and black clothing will absorb this radiation.

3) The shiny suits will reflect the strong heat radiation from the sun so the astronauts do not overheat.

4) Insulation is a poor heat conductor and it contains glass pieces to reflect heat back into your home.

5) In summer, heat is reflected out into the environment and in winter, heat is reflected back into your home.

Thermal Energy Transfer: Convection

Convection

·        Convection - The transfer of thermal energy by moving particles in fluids

·        As the particles of fluids (gases and liquids) are heated, they move faster and expand; this expansion makes the fluids less dense so they rise

·        When warmer fluids rise, cooler fluids move downwards; this creates a “convection current”

·        The convection current continues in a pot of soup because the warmer soup particles in a pot cool when they make contact with the air and then sink. These particles are heated again once they meet the bottom of the pot.

·        Convection currents help heat your home through your furnace heating system.

Thermal Energy Transfer: Conduction

Conduction

·        The transfer of heat through a solid or between a solid and another solid, a liquid, or a gas that is in contact with it

·        Conduction can also occur from liquid to solid and gas to solid.

·        Conduction always occurs from a warmer region to a cooler region.

·        Conduction occurs when warmer particles bump into cooler particles making them vibrate faster.

·        Metals are better heat conductors than non-metals because free electrons carry heat quickly through the material.

Answers to Conduction Worksheet

On a cold winter day, why would an iron post in a park feel much colder to the touch than a wooden bench?

Iron is a better heat conductor than wood. The iron will conduct the heat away from your hand faster than wood; this makes your hand feel colder when you touch iron

Potatoes cook from the outside in.

a)     Why does a small potato cook faster than a large potato?

Smaller potatoes have fewer particles, so heat takes less time to reach the centre.

b)    Why does sticking a metal skewer through the middle of a potato make it cook faster?

Heat will be conducted through the skewer into the centre of the potato and it will cook from the inside out.

Eureka Expansion and Contraction Video

Here is the video we viewed in class.

Expansion and Contraction Worksheet Answers

Solids Expanding and Contracting in our Daily Lives

1.   Why is it important to place gaps at regular intervals in sidewalks?

In the summer the sidewalk expands and in the winter it contracts. The gaps allow space for the expansion and contraction so the sidewalk doesn’t crack.

2.   Steel bolts used to connect things together are sometime heated and put in place while they are still hot. Why?

When hot, the length of the bolts increases. So when they cool, they pull together the parts they are fastening.

3.   Concrete and steel expand at almost the same rate. Explain why this is important in the construction of tall buildings.

If they did not expand and contract at the same rate, there would be many cracks in the building and it might fall down.

Gases Expanding and Contracting in our Daily Lives

1.   Explain how a hot air balloon is lifted from the ground.

When the gas particles inside the hot air balloon are heated, they expand and some escape from the bottom of the balloon. This causes there to be fewer air particles inside the balloon then outside the balloon. The less dense hot air will float on more dense cold air so the balloon rises.

c) Once in the air, the burner is turned off and the balloon drifts along with the wind. What will eventually happen to the air inside the balloon?

Cooler air will enter the balloon and the air inside will become more dense. The balloon will begin to go down.

Liquids Expanding and Contracting in our Daily Lives

1.   A bowl of hot soup was left on the table to cool. After a few minutes, the amount of soup in the bowl appeared to have decreased? Why?

Some of the soup may have evaporated or the soup may have cooled down and there seems to be less soup because the particles become closer together (contract) and become denser.

2.   When manufacturers pack liquids into bottles and jars, they leave a small space at the top before putting on the lids. Why?

The space allows for the liquid to expand without causing the bottle to break.

3.   Mercury expands and contracts faster than alcohol. Which liquids would be better in a thermometer?

Mercury will tell the temperature faster, but it will also contract faster so it will drop more quickly making it harder to read the temperature. Also, mercury is poisonous!

Materials for Putt Putt Boats

Please collect the following materials at home for the Putt Putt Boat project. If you are working in pairs only one set of materials is required.

1. One or more empty pop cans (standard size); they must have absolutely no dents
2. One 2L carton of milk or juice
3. One empty cereal box
4. One shoebox or other box to store materials