Answer:
Answer D. Picture II shows a chemical change, because the same substance changes form
Explanation:
This is the temperature that water molecules slow down enough to stick to each other and form a solid crystal
Answer with Explanation:
A candle relights when a match is held above the wick because its trail of smoke still contains some of the wax. When candles are burned, the heat of the flame turns the the wax (which is originally solid) into liquid (commonly near the wick) and then evaporates as gas. The vaporized wax actually protect the wick and this is the reason why it is not burned. So, when you put off a candle, the vaporized wax is still present near the wick. This, remember, holds heat and light energy. Thus, this explains why the candle can be relighted once you hold a match above the wick. It then allows the match to ignite.
Thus, this explains the answer.
Answer is "C".
<em><u>Explanation
</u></em>
Single replacement reaction is a type of reaction which one reactant reacts with another and makes a product by replacing one element by another.
Mg (Magnesium) reacts with Al₂O₃ (Aluminium oxide) and produces MgO (Magnesium oxide) and Al (Aluminium) as products. Here Al is replaced by Mg. Reaction is
Mg + Al₂O₃ → MgO + Al
To balance the reaction equation, both left and right hand sides should have same number of atoms in each element.
Here,
<em>Left Hand Side has </em> <em>Right Hand Side has</em>
Mg = 1 atom Mg = 1 atom
Al = 2 atom Al = 1 atom
O = 3 atom O = 1 atom
First step : balance the O atoms in both sides. To do that "3" should be added before MgO.
Second step : After balancing O atoms, there will be 3 Mg atoms in right hand side. Hence to balance Mg atoms again "3" should be added before Mg in left hand side
Third step : as the final step balance the Al atoms by adding "2" before Al in the right hand side.
Then final balanced equation should be
3Mg + Al₂O₃ → 3MgO + 2Al
Answer:
0.1313 g.
Explanation:
- It is known that at STP, 1.0 mole of ideal gas occupies 22.4 L.
- Suppose that hydrogen behaves ideally and at STP conditions.
<u><em>Using cross multiplication:</em></u>
1.0 mol of hydrogen occupies → 22.4 L.
??? mol of hydrogen occupies → 1.47 L.
∴ The no. of moles of hydrogen that occupies 1.47 L = (1.0 mol)(1.47 L)/(22.4 L) = 6.563 x 10⁻² mol.
- Now, we can get the no. of grams of hydrogen in 6.563 x 10⁻² mol:
<em>The no. of grams of hydrogen = no. of hydrogen moles x molar mass of hydrogen</em> = (6.563 x 10⁻² mol)(2.0 g/mol) = <em>0.1313 g.</em>
Answer:
There are five signs of a chemical change:
Colour Change.
Production of an odour.
Change of Temperature.
Evolution of a gas (formation of bubbles)
Precipitate (formation of a solid).
